Straight Pipe?
Thread Starter
|
Freshman User
Joined: May 2010
Posts: 38
Likes: 0
Straight Pipe?
Well she ain't sold yet and I haven't gotten much interest recently, and I've been dying to do some wrenchin, and my neighbor is pissing me off and hates the "noise" my truck makes... so I'm thinkin it's time to straight pipe it 
.
Currently it's 4" turbo-back, cat but no muffler, dumps in front of the rear wheel right at the edge of the wheel well.
I've straight piped vehicles in the past but they were all gas burners, so I've got a couple questions. I've been searching around on google and have come up with some conflicting info.
1. First off, is this even ok to do? I've heard that a 4" straight pipe won't give me enough backpressure, but then I've also heard that the turbo creates enough bp that in theory I could run with just the downpipe.
2. Logic (or my version of it) says that a more free-flowing exhaust will lower my EGTs, produce thicker smoke without the cat, the turbo will spool quicker, and should result in a little more power and better acceleration off the line... not directly, but the quicker spool time will. But then I've read that a straight pipe on a 7.3 will obviously sound better, but that it'll give you no actual benefits like EGTs and whatnot... but that doesn't make sense to me. So what's your guys' imput on this?
3. For the cat delete, which is really all I'm doing, I see 2 options: 1) Get a 4" pipe and swap it in, so it'll just be one long stretch of 4" pipe, or 2) Use a larger piece of pipe, maybe 5" or 6", to act as sort of a resonator. Thoughts?
I know I could always just gut the cat, but I'd like to keep it intact for when emissions time rolls around.
Thanks!
.Currently it's 4" turbo-back, cat but no muffler, dumps in front of the rear wheel right at the edge of the wheel well.
I've straight piped vehicles in the past but they were all gas burners, so I've got a couple questions. I've been searching around on google and have come up with some conflicting info.
1. First off, is this even ok to do? I've heard that a 4" straight pipe won't give me enough backpressure, but then I've also heard that the turbo creates enough bp that in theory I could run with just the downpipe.
2. Logic (or my version of it) says that a more free-flowing exhaust will lower my EGTs, produce thicker smoke without the cat, the turbo will spool quicker, and should result in a little more power and better acceleration off the line... not directly, but the quicker spool time will. But then I've read that a straight pipe on a 7.3 will obviously sound better, but that it'll give you no actual benefits like EGTs and whatnot... but that doesn't make sense to me. So what's your guys' imput on this?
3. For the cat delete, which is really all I'm doing, I see 2 options: 1) Get a 4" pipe and swap it in, so it'll just be one long stretch of 4" pipe, or 2) Use a larger piece of pipe, maybe 5" or 6", to act as sort of a resonator. Thoughts?
I know I could always just gut the cat, but I'd like to keep it intact for when emissions time rolls around.
Thanks!
Posting Guru
Joined: Mar 2007
Posts: 1,842
Likes: 2
From: hillsborough nj
1. First off, is this even ok to do? I've heard that a 4" straight pipe won't give me enough backpressure, but then I've also heard that the turbo creates enough bp that in theory I could run with just the downpipe.
the turbo creates enough back pressure, don't be worried about that
2. Logic (or my version of it) says that a more free-flowing exhaust will lower my EGTs, produce thicker smoke without the cat, the turbo will spool quicker, and should result in a little more power and better acceleration off the line... not directly, but the quicker spool time will. But then I've read that a straight pipe on a 7.3 will obviously sound better, but that it'll give you no actual benefits like EGTs and whatnot... but that doesn't make sense to me. So what's your guys' imput on this?
free-flowing exhaust will lower EGTs, raise boost a tad, only increase visible smoke because of the lack of a cat, and will enhance spool up... you may notice a tiny power difference but that can be attributed to the quicker spool up and thus more torque which means more power early in the rpm band
3. For the cat delete, which is really all I'm doing, I see 2 options: 1) Get a 4" pipe and swap it in, so it'll just be one long stretch of 4" pipe, or 2) Use a larger piece of pipe, maybe 5" or 6", to act as sort of a resonator. Thoughts?
just use the same size pipe you have, whether its 4" or 3.5" or whatever, try to keep the size the same... if you make the size get larger then smaller then larger again, or vice versa, it'll just limit flow due to turbulence
I know I could always just gut the cat, but I'd like to keep it intact for when emissions time rolls around.
Thanks!
the turbo creates enough back pressure, don't be worried about that
2. Logic (or my version of it) says that a more free-flowing exhaust will lower my EGTs, produce thicker smoke without the cat, the turbo will spool quicker, and should result in a little more power and better acceleration off the line... not directly, but the quicker spool time will. But then I've read that a straight pipe on a 7.3 will obviously sound better, but that it'll give you no actual benefits like EGTs and whatnot... but that doesn't make sense to me. So what's your guys' imput on this?
free-flowing exhaust will lower EGTs, raise boost a tad, only increase visible smoke because of the lack of a cat, and will enhance spool up... you may notice a tiny power difference but that can be attributed to the quicker spool up and thus more torque which means more power early in the rpm band
3. For the cat delete, which is really all I'm doing, I see 2 options: 1) Get a 4" pipe and swap it in, so it'll just be one long stretch of 4" pipe, or 2) Use a larger piece of pipe, maybe 5" or 6", to act as sort of a resonator. Thoughts?
just use the same size pipe you have, whether its 4" or 3.5" or whatever, try to keep the size the same... if you make the size get larger then smaller then larger again, or vice versa, it'll just limit flow due to turbulence
I know I could always just gut the cat, but I'd like to keep it intact for when emissions time rolls around.
Thanks!
Thread Starter
|
Freshman User
Joined: May 2010
Posts: 38
Likes: 0
And yeah I've seen that done before, and that'll pass a visual inspection, but where I live (Denver) they also do a particulate test where they shine a light through your exhaust and see how much of the light passes through, so I think without a cat I'd fail that one.
Thread
Thread Starter
Forum
Replies
Last Post
BlueOvalBud
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
13
Dec 26, 2010 05:47 PM
spdmpo
1999 - 2003 7.3L Power Stroke Diesel
4
Nov 26, 2010 08:52 AM
